CHAPTER 1

What Is Coding?

You know that coding has to do with building the apps you use and controlling the technology in your life, but what exactly is coding? Coding, also known as computer programming, is creating instructions for a computing device to do something. You use a language to communicate with other people, and computers use a coding language to communicate. And just as you can learn to write, speak, and understand languages different from the one you first learned as a toddler, you can learn to communicate in a coding language - so that you can "talk to" computers!

You're probably wondering whether coding is hard to learn. The answer is that it's easy to get started with coding, and easy to write real computer programs to perform all sorts of tasks! Unlike the early days of coding, when computer programmers talked to computers using long sequences of numbers (0s and 1s), you can now write code by using words and symbols that you can understand easily. For example, you can tell an app to play a sound three times ("boom boom boom!") with a command such as repeat 3 (play sound boom). Neat, huh?

This type of human-friendly coding, which is called a high-level language, is what you will use when you're first learning to code. (Many professional programmers also use high-level languages.) Later, I talk more about high-level languages and the languages you'll use in this book.

You're probably also wondering whether you can make anything cool as a new coder. Yes, you can! In this book, you write code to build games, toys, and electronic gadgets. Everything you create you can play with and share with your friends and family.

What Languages Will I Use?

This book is filled with great projects you can do to learn the basics of coding and make real apps. You'll be using two programming languages to code: Scratch and JavaScript.

In the Scratch language, you build code with blocks (also called tiles) that snap together to make complete programs. Scratch is a learning language, created especially for kids, and has its own integrated development environment (IDE), which is a fancy name for a place where you write and test code.

JavaScript is a professional programming language that real coders use to make all sorts of things from apps to websites. You will use two easy-peasy IDEs to code in JavaScript: App Lab and MakeCode. As with the Scratch IDE, these JavaScript IDEs let you work in block mode, snapping together your coding commands. But when you feel ready to tackle text-based coding - typing your commands - you can switch to text mode in App Lab and MakeCode.

You can create your code in Scratch, App Lab, and MakeCode on any computer or tablet. Just be sure you have a good Internet connection, and you're ready to go! You learn more about the basics of working with each language and programming environment in Chapter 2.

What Does a Computer Program Look Like?

A computer program consists of the instructions you code to make a computer do something. A program looks like a list of steps, filled with words and symbols. Many words in the list will be familiar, such as for, if, and forever. Words in a computer program are called commands because you're commanding the computer to perform some sort of action. Some commands look like combinations of words you know, smushed together into new words. For example, JavaScript uses the onEvent command to find out whether a user has pressed a button.

You might also recognize many of the symbols in a computer program. These look like operators you use in math class (+, -, >. =) and also like punctuation marks you use in English class, such as a period (.) and a semicolon (;).

All of the commands and symbols in a computer program are organized in a special order so that the computer can understand what it is supposed to do. Planning that order and then coding it is a bit like writing an essay, solving a math problem, performing dance choreography, or running a play in football. You have to put together and execute (run) the program in a specific order - you can't just put the instructions anywhere and expect the program to work correctly.

A Hello World! Example

Historically, the first computer program a new coding student writes is one that prints the words "Hello World!" on the computer screen. Figure 1-1 shows an example of what that code looks like in Scratch, and its resulting output (what it displays onscreen).

Figure 1-1

Figure 1-2 shows the same code in JavaScript (in block mode and in text mode) using the App Lab IDE, and its resulting output.

Figure 1-2

Figure 1-3 shows the same code in JavaScript (in block mode and in text mode) using the MakeCode IDE, and the output when displayed on the micro:bit electronics board. Because the micro:bit can scroll only one letter at a time, the figure displays only the letter H at the beginning of "Hello World!"

Figure 1-3

You'll be making little programs like this, and much bigger programs too, in no time!

Recipe for a Program

Many mornings, I cook chocolate chip pancakes for my family, following a recipe I created myself. A recipe is like a computer program, and following the recipe is like executing the program. The recipe has parts, including gathering and measuring ingredients, mixing the ingredients to make the pancake batter, and then dropping spoonfuls of the batter onto the griddle to cook it. Similarly, a computer program has parts such as asking the user for information, doing something with that information, and then telling the user the result.

Within each part of a program, you write small chunks of code to perform different processes. A chunk of code that performs a task is called an algorithm. For example, one algorithm I perform when making pancakes is testing the surface temperature of the griddle: I plug in the griddle, set it to a certain temperature, and drip a few droplets of water onto the surface to see how quickly they evaporate.

Constructing algorithms is important in coding programs to run on a computer. Think about the types of algorithms you might make in a favorite game you play on your phone. For instance, an algorithm you might code in a Yahtzee game is rolling the dice. Or an algorithm you might code in a Space Invaders game is flying a spaceship across the sky every so often.

The algorithms you create connect with each other to build your entire program. As coders, we have three fancy terms to describe how our algorithms connect: sequence, selection, and repetition. Here's what each means:

• Sequence: The order in which a process is conducted. Every computer program must be organized so that steps are executed in a logical order. For example, when making pancakes, I must run my algorithm for making batter before running my algorithm for cooking the batter!
• Selection: Choosing a path based on certain conditions. For example, when choosing a movie to attend this weekend, you might decide between an action movie or a comedy. The decision you make then directs you to new sequences - and, consequently, other selections - that relate to your choice. Selection is often coded using conditional statements structured this way: if [condition occurs] then [consequence occurs]. These conditional commands let you create as many paths as needed to respond to the conditions of the program.
• Repetition: The process of repeating something. When you repeat code, you make it loop over and over again. A loop is a structure that tells the computer to run the same commands multiple times, without the need to rewrite those same commands. You already know how loops work: In a song, the drumbeat is looped to provide a continuous rhythm pattern from the first note of the song to the last.

Throughout the book, you'll see references to sequence, selection, and repetition. Check back here to refresh your memory of how each is used when coding a program.

Planning a Program

As you plan and develop your programs, you'll need to have some organized way of writing them down. You can use several methods to represent a program before you translate it into code for use on a computer.

Some people like to draw a picture or a series of pictures (called a storyboard) to show how an app, a game, or a website will look onscreen. This type of work is often performed by graphic designers, the people who make the images and the animations for computer programs. You will be doing your own graphic design work for the programs you code in this book, so think about doing a little drawing before you touch the keyboard to code.

Other people like to build a flowchart or write pseudocode when planning their programs. A flowchart is like a little map with special boxes and arrows that describe the main parts of the program. Table 1-1 shows some of the most important flowchart symbols and what each symbol...